JP2014132736A - Information processing system and method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress communication traffic between first and second devices when verifying alteration of a document image in an information processing system including the first and second devices.SOLUTION: An input unit 301 inputs a document image, and a background pattern extraction unit 302 extracts a background pattern from the document image. From the background pattern, a decoding unit 307 decodes position information and an amount of feature of a predetermined area in the document image. A partial image transmitter unit 305 extracts as a partial image an image in the document image area corresponding to the position information. An alteration detector unit 310 extracts the amount of feature of the partial image, and compares the extracted amount of feature with the decoded amount of feature, to verify the alteration of the document image area corresponding to the position information.

Description

  The present invention relates to a document image modification verification process.

  Various methods have been proposed as print document protection techniques for verifying the presence or absence of alterations such as falsification and additional writing of a print document (see Patent Document 1).

  In the protection technique of Patent Document 1, when printing a document image, the position information of the protection region in the document image and the dot arrangement pattern representing the average luminance as the feature amount of the protection region are embedded in the entire background of the document image. In verification, the arrangement pattern of the dots embedded in the printed document is read, the position information and the average brightness of the protected area are decoded, and whether the average brightness of the protected area is varied or not is altered. Is detected. The protected area is a specific area in the document image to be protected from modification, and detection of modification of this area is the purpose of the protection technique for the printed document.

  When the protection technology disclosed in Patent Document 1 is implemented using a cloud or server, the entire document image must be transmitted to the server even though the protected area is a part of the document image. There is a huge problem.

  Further, when the protection technique disclosed in Patent Document 1 is applied to a client-server system, the client transmits image data of a print document read by a scanner or the like to the server. The server obtains the feature quantity of the protection area from the dot arrangement pattern and barcode of the received image data, and compares the obtained feature quantity with the feature quantity of the original protection area to verify the modification of the protection area. become.

  In the verification, the server cannot specify the position and shape of the protection area unless it reads the dot arrangement pattern of the entire image data, and the image data of the entire printed document is required. On the other hand, for example, when detecting a change in the answer column of a questionnaire form or the prescription amount of a prescription drug, it is sufficient to set a partial area of the document as a protected area. However, even in such a case, it is necessary to transmit the image data of the entire printed document from the client to the server in order to specify the position and shape of the protected area.

JP 2008-211769 A

  An object of the present invention is to suppress communication traffic between a first device and a second device when verifying modification of a document image in an information processing system including the first and second devices.

  The present invention has the following configuration as one means for achieving the above object.

  The information processing according to the present invention includes an input unit, a background pattern extraction unit, a decoding unit, a partial image extraction unit, a feature amount extraction unit, and a verification unit that are distributed in the first and second apparatuses. In the system, a document image is input, a background pattern is extracted from the document image, position information and a feature amount of a predetermined area of the document image are decoded from the background pattern, and the document image corresponding to the position information is decoded. Extracting an image of a region as a partial image, extracting a feature amount of the partial image, comparing the extracted feature amount with the decoded feature amount, and modifying the region of the document image corresponding to the position information It is characterized by verifying.

  ADVANTAGE OF THE INVENTION According to this invention, when verifying the modification | change of a document image in an information processing system provided with a 1st and 2nd apparatus, the communication traffic between a 1st and 2nd apparatus can be suppressed.

The block diagram explaining the structural example of the information processing system of an Example. The block diagram which shows the structural example of a general purpose computer. FIG. 2 is a block diagram illustrating an example of a functional configuration of the image processing system according to the embodiment. The figure explaining embedding of a background pattern and acquisition of the information of a protection area. The flowchart explaining the change detection process in the information processing system of an Example. FIG. 9 is a block diagram for explaining an example functional configuration of an image processing system according to a first modification. 10 is a flowchart for explaining alteration detection processing in the information processing system according to the first modification. FIG. 9 is a block diagram for explaining an example functional configuration of an image processing system according to a second modification. 10 is a flowchart for explaining alteration detection processing in the information processing system according to the second modification.

  Hereinafter, information processing according to an embodiment of the present invention will be described in detail with reference to the drawings.

[System configuration]
A configuration example of the information processing system of the embodiment will be described with reference to the block diagram of FIG.

  An information processing system 100 shown in FIG. 1A includes an image processing device (first device) 101 and an image processing device (second device) 102, and the two devices are connected to each other via a network 105. , Send and receive data. The image processing apparatus 101 is, for example, a multifunction peripheral (MFP) 103 that prints a document image or reads a printed document, and the image processing apparatus 102 is a server 104 that detects modification of a print document based on information received from the MFP 103, for example. .

  Alternatively, as shown in FIG. 1B, the first image processing apparatus 101 may be configured by a personal computer (PC) 106, a scanner 107, and a printer 108 instead of the MFP 103. Further, the first image processing apparatus 101 may be configured using the MFP 103 instead of the scanner 107 and the printer 108.

  As the network 105, Ethernet (registered trademark), a wired network using a serial bus such as USB or IEEE1394, a wireless network such as IEEE802.11 or Bluetooth (registered trademark), or the like can be used.

  A configuration example of the general-purpose computer 200 is shown in the block diagram of FIG. The general-purpose computer 200 can be used as the server 104 or the PC 106.

  In the general-purpose computer 200, the CPU 201 executes a program stored in the ROM of the memory 203 or the hard disk drive (HDD) 207 using the RAM of the memory 203 as a work memory, and controls all or part of the operation of the general-purpose computer.

  The memory 203 is connected to the CPU 201 via the memory controller hub 204, and is used for primary storage such as storage of a program executed by the CPU 201 and data that changes as appropriate when the program is executed.

  The video controller 202 is connected to the CPU 201 via the memory controller hub 204, and displays an image, a user interface (UI), and the like on an output device 210 such as a monitor according to the control of the CPU 201.

  The HDD 207 is connected to the CPU 201 via the input / output controller hub 205 and the memory controller hub 204. The HDD 207 is used for storing programs executed by the CPU 201 and data necessary for executing the programs, and storing image data and program execution results.

  A network interface card (NIC) 206 is a communication interface connected to a communication path such as the network 105. The CPU 201 communicates with various computer devices connected to the network 105 via the NIC 206.

  The external connection port 208 is a port for connecting the peripheral device 209 to the general-purpose computer 200, such as a USB port, an IEEE1394 port, or an HDMI port. The general-purpose computer 200 can transmit and receive data to and from the peripheral device 209 connected to the external connection port 208. The peripheral device 209 includes, for example, an input device such as a keyboard and a mouse, an image input device such as a digital camera and a scanner, an image output device such as a printer and a monitor, and an MFP.

[Function configuration]
A functional configuration example of the image processing system of the embodiment will be described with reference to the block diagram of FIG.

  In the image processing apparatus 101, an input unit 301 inputs a document image of a print document read by a scanner, a document image of PDF data, and the like. The background pattern extraction unit 302 extracts the background pattern of the input document image as an image. The background pattern corresponds to a visible image used for embedding information in the background of the document image, such as a dot arrangement pattern or a barcode. The background pattern transmission unit 303 transmits the extracted background pattern to the image processing apparatus 102.

  In the image processing apparatus 102, the background pattern receiving unit 306 receives a background pattern from the image processing apparatus 101. The decoding unit 307 decodes the received background pattern, and acquires the position information of the protected area and the feature amount of the protected area in the document image.

  Background pattern decoding is a process of extracting embedded information from a background pattern, and the decoding method differs depending on the type of background pattern. The feature amount is a feature amount of the original, and is, for example, an average luminance or a frequency component of the pixels in the original protected area. The position information is information for specifying the position and rectangular size of the protection area, and is, for example, the coordinates of the upper left pixel and the lower right pixel of the protection area.

  The position information transmission unit 308 transmits the position information of the protected area extracted from the background pattern to the image processing apparatus 101. The position information receiving unit 304 receives position information of the protected area from the image processing apparatus 102. The partial image transmission unit 305 identifies a protected area in the document image from the received position information of the protected area, and transmits a partial image corresponding to the identified area to the image processing apparatus 102.

  The partial image receiving unit 309 receives a partial image from the image processing apparatus 101. The alteration detection unit 310 extracts the feature amount of the received partial image, compares the extracted feature amount with the feature amount acquired by the decoding unit 307, and verifies whether the document image has been altered such as falsification or additional writing. . The verification result transmitting unit 311 transmits the verification result of modification to the verification result receiving unit 312 of the image processing apparatus 101.

  As described above, each functional block is distributed and arranged in the image processing apparatus 101 and the image processing apparatus 102, and functions as an information processing system that verifies whether or not there is a modification by transmitting and receiving data to and from each other. Although details will be described later, in which device each functional block is arranged is not limited to the example in FIG.

[Embed background pattern]
Hereinafter, as an example, a method of embedding a background pattern in a document image as a dot arrangement pattern will be described. The embedding of the background pattern is not limited to the dot arrangement pattern, and a bar code or other background pattern can also be used. The background pattern embedding and protection area information acquisition will be described with reference to FIG.

  The user operates the UI to designate the protection area of the document image 701. FIG. 4A shows an example in which a rectangular area 702 surrounding the character “C” is designated as a protection area. The CPU 201 acquires position information indicating the position and shape of the protection area 702 and the feature amount of the protection area 702 as information of the protection area 702. The position information is, for example, the coordinates 703 of the upper left pixel and the coordinates 704 of the lower right pixel of the protection area 702. The feature amount is, for example, an average value (average luminance) of luminance values of pixels included in the protection region 702.

  Next, the CPU 201 divides the document image 701 into a plurality of square areas 706 as shown in FIG. Then, with the center of the square area 706 as a reference, for example, when a dot is placed in the upper left corner of the area (example of reference numeral 707), the value is 0, and when a dot is placed in the center of the upper end, the value is 1, and the upper right corner is A value represented by each square area 706 is defined as a value 2 when a dot is hit. In the example of Fig. 4 (B), the value in the upper left corner is 0, the value in the upper center is 1, the value in the upper right corner is 2, the value in the right center is 3, the value in the lower right corner is 4, and the value in the lower center is clockwise. 5, the lower left corner has a value of 6, and the center of the left side has a value of 7. However, as long as the embedding rule indicating the relationship between the dot position and the value is defined, the relationship is not limited to the relationship shown in FIG.

  That is, the CPU 201 generates a document image 708 in which the information on the protection area 702 is embedded in the document image 701 by placing one dot in each square area 706 according to the information on the protection area 702.

  FIG. 4C illustrates a method for acquiring information on the protected area 702 from the document image 709. The document image 709 shows an example in which the character “C” of the document image 708 in which the background pattern is embedded is changed to “D”. The CPU 201 extracts the background pattern 710 from the document image 709, obtains the value indicated by each square area from the position of the dot in the square area in accordance with the embedding rule of the dot arrangement pattern, and decodes the protection area information 711.

  Next, the CPU 201 specifies the area 712 of the document image 709 from the acquired position information of the protected area, and acquires the feature amount of the specified area. Then, the feature quantity indicated by the protected area information 711 is compared with the feature quantity acquired from the area 712, and if the feature quantity difference is within a predetermined range, it is determined that there is no modification, and the feature quantity difference is predetermined. If it exceeds the range, it is determined that “altered”.

[Modification detection processing]
Modification detection processing in the information processing system of the embodiment will be described with reference to the flowchart of FIG.

  The input unit 301 of the image processing apparatus 101 inputs image data of a document image in accordance with a user instruction via the UI (S401). The background pattern extraction unit 302 extracts a background pattern from the image data (S402), and converts the extracted background pattern into a binary image (S403). The background pattern transmission unit 303 transmits the binary image data of the background pattern to the image processing apparatus 102 (S404). The background pattern may be transmitted as multi-valued image data, but color information and gradation information are not required for decoding the background pattern, and whether or not dots are formed in each square area ( It is only necessary to know the dot on / off state. Therefore, the background pattern is binarized in order to compress the data size and reduce the amount of communication traffic.

  Next, the background pattern receiving unit 306 of the image processing apparatus 102 receives binary image data from the image processing apparatus 101 (S411). The decoding unit 307 decodes the position information and feature amount of the protection area from the received binary image data (S412). The position information transmission unit 308 transmits the decoded position information of the protection area to the image processing apparatus 101 (S413).

  Next, the position information receiving unit 304 of the image processing apparatus 101 receives the position information of the protection area from the image processing apparatus 102 (S405). The partial image transmission unit 305 cuts out the image data of the area corresponding to the received position information of the protected area from the image data of the document image, and transmits the cut out image data (partial image data) to the image processing apparatus 102 (S406). ).

  The partial image receiving unit 309 of the image processing apparatus 102 receives partial image data from the image processing apparatus 101 (S414). The modification detection unit 310 acquires the same type of feature quantity as the feature quantity decoded in step S412 from the received partial image data (S415), and compares both feature quantities (S416). When the decoded feature amount is the average luminance, the feature amount acquired in step S415 is also the average luminance.

  As a result of comparing the feature quantities (S416), the alteration detection unit 310 determines that the protected area is not altered if the difference between the decoded feature quantities and the feature quantities acquired from the partial image data is within a predetermined range ( S417). If the difference exceeds the predetermined range, it is determined that the protected area is altered (S418).

  The verification result transmission unit 311 transmits the verification result of whether or not there is a modification to the image processing apparatus 101 (S419), and the verification result reception unit 312 receives the verification result of whether or not there is a modification (S407). The verification result of the presence / absence of alteration is displayed on the UI by the CPU 201 of the image processing apparatus 101, for example.

  As described above, when verifying the modification of the print document in the server, it is not necessary to transmit the entire document image of the print document by using the data transmitted from the client to the server as the partial image data of the background pattern and the protection area. As a result, the amount of communication traffic between the client and server can be suppressed.

[Modification 1]
Below, the modification which switches a process with the data size of a document image is demonstrated.

Functional Configuration An example of the functional configuration of the image processing system according to the first modification will be described with reference to the block diagram of FIG. 6 differs from the configuration shown in FIG. 3 in that a switching unit 313 is added to the image processing apparatus 101. The switching unit 313 determines whether the data size of the input document image is equal to or smaller than a predetermined size, and outputs the determination result to the background pattern extraction unit 302.

  When the determination result indicating that the data size of the document image exceeds the predetermined size is input from the switching unit 313, the background pattern extraction unit 302 extracts the background pattern from the image data of the document image. The same processing is executed.

  On the other hand, when the determination result indicating that the data size of the document image is equal to or smaller than the predetermined size is input from the switching unit 313, the background pattern extraction unit 302 does not extract the background pattern from the image data of the document image. Then, the image data of the document image to which the information (all image flag) indicating the image data of the document image is added is output to the background pattern transmission unit 303.

  When the image processing apparatus 102 receives the image data with the all-image flag added by the background pattern receiving unit 306, the image processing apparatus 102 decodes the information of the protection area, extracts the image data of the protection area, and whether or not there is any alteration by the received image data. Perform verification. That is, the presence / absence of modification is verified without transmitting position information and receiving partial image data with the image processing apparatus 101.

  Hereinafter, processing of each unit of the image processing apparatus 102 when image data to which all image flags are added is received will be described.

  The decoding unit 307 extracts a background pattern from the received image data, and decodes information on the protection area from the background pattern.

  The alteration detection unit 310 extracts a feature amount from image data corresponding to the protected area of the received image data, compares the extracted feature amount with the feature amount acquired by the decoding unit 307, and performs falsification or additional writing on the document image. Verify whether or not there is any modification. The verification result transmission unit 311 transmits the verification result of the presence / absence of modification to the verification result reception unit 312 of the image processing apparatus 101.

Modification Detection Processing Modification detection processing in the information processing system according to the first modification will be described with reference to the flowchart in FIG. The processing when the data size of the document image exceeds a predetermined size is the same as that in FIG. 5, and FIG. 7 mainly shows the processing when the data size of the document image is equal to or smaller than the predetermined size.

  The input unit 301 of the image processing apparatus 101 inputs image data of a document image in accordance with a user instruction via the UI (S401). The switching unit 313 determines whether the data size of the input image data is equal to or smaller than a predetermined size, and outputs the determination result to the background pattern extraction unit 302 (S421).

  If the determination result indicates that the size exceeds a predetermined size, the same processing as in FIG. 5 is executed. On the other hand, when the determination result is equal to or smaller than the predetermined size, the background pattern extraction unit 302 outputs the image data of the document image to which the all image flag is added to the background pattern transmission unit 303, and the background pattern transmission unit 303 outputs the image data. The image is transmitted to the image processing apparatus 102 (S422).

  The background pattern receiving unit 306 of the image processing apparatus 102 receives the image data (S431), and determines whether or not all image flags are added to the received image data (S432).

  If all the image flags are not added, the same processing as in FIG. 5 is executed. On the other hand, when all the image flags are added, the decoding unit 307 extracts a background pattern from the received image data (S433), and decodes information on the protection area from the background pattern (S434). The alteration detection unit 310 acquires the same type of feature quantity as the feature quantity decoded in step S434 from the image data corresponding to the feature area of the received image data (S435).

  Thereafter, the processing is the same as in FIG. 5, but the modification detection unit 310 compares both feature amounts (S416), and the difference between the decoded feature amount and the feature amount acquired from the image data corresponding to the feature region is If it is within the predetermined range, it is determined that the protected area is not altered (S417). If the difference exceeds the predetermined range, it is determined that the protected area is altered (S418). Then, the verification result transmission unit 311 transmits the verification result of whether or not there is a modification to the image processing apparatus 101 (S419), and the verification result reception unit 312 receives the verification result of whether or not there is a modification (S407).

  The threshold value (predetermined size) of the data size of the document image may be a fixed value. However, a threshold value setting unit (not shown) is provided in the image processing apparatus 101 so that it can be operated according to the communication amount and calculation performance of the image processing apparatus 101. Alternatively, a threshold value may be set. By switching the process according to the data size of the document image, if there is a margin in communication volume, the entire image data of the document image is transmitted to the image processing apparatus 102, and the process leading to verification of the presence / absence of modification is simplified. Efficient processing can be realized.

  Further, when the calculation performance of the image processing apparatus 101 is low, it is more efficient for the image processing apparatus 102 to perform the processing of steps S433 to S435 with a large processing load, and the threshold value is determined accordingly. For example, if there is a margin of 100 megabytes in the communication amount and the calculation performance of the image processing apparatus 101 is sufficiently high, the threshold is set to 90-100 megabytes. On the other hand, when the calculation performance of the image processing apparatus 101 is low, the threshold is set to 1-10 megabytes so that most of the processing related to the document image having a large data size is imposed on the image processing apparatus 102.

[Modification 2]
Hereinafter, a modification example in which the image processing device 101 extracts the feature amount of the image data corresponding to the protection area and transmits the extracted feature amount to the image processing device 102 will be described. According to the second modification, the amount of computation in the image processing apparatus 101 increases, but the data size of the feature amount is extremely small compared to the partial image data (for example, 8-bit data representing average luminance), and the communication traffic amount is reduced. Can be suppressed.

Functional Configuration An example of the functional configuration of the image processing system according to the second modification will be described with reference to the block diagram of FIG. The configuration of FIG. 8 differs from the configuration shown in FIG. 3 in that the image processing apparatus 101 has a feature quantity extraction unit 314 and a feature quantity transmission unit 315 instead of the partial image transmission unit 305, and the image processing apparatus 102 has a partial configuration. The feature receiving unit 316 is provided instead of the image receiving unit 309.

  The feature amount extraction unit 314 of the image processing apparatus 101 identifies the image data of the document image corresponding to the protection area based on the position information of the protection area received by the position information reception unit 304, and extracts the feature amount of the image data. To do. The feature amount transmission unit 315 transmits the feature amount input from the feature amount extraction unit 314 to the image processing apparatus 102.

  The feature amount receiving unit 316 of the image processing apparatus 102 receives the feature amount of the image data corresponding to the protected area from the image processing apparatus 101. The alteration detection unit 310 verifies the alteration by comparing the received feature amount with the feature amount decoded by the decoding unit 307.

Modification Detection Processing Modification detection processing in the information processing system according to the second modification will be described with reference to the flowchart in FIG. Note that the same reference numerals are assigned to processes substantially similar to those in FIG. 5, and detailed description thereof is omitted.

  The processing from the image input (S401) to the position information reception (S405) in the image processing apparatus 101, and the background pattern reception (S411) to the position information transmission (S413) in the image processing apparatus 102 are the same as in FIG. . When the position information receiving unit 304 receives the position information, the feature amount extraction unit 314 identifies image data of the document image corresponding to the protected area based on the received position information, and extracts the feature amount of the image data. (S441). The feature amount transmission unit 315 transmits the feature amount input from the feature amount extraction unit 314 to the image processing apparatus 102 (S442).

  The feature amount receiving unit 316 of the image processing apparatus 102 receives the feature amount from the image processing apparatus 101 (S451). The alteration detection unit 310 compares the feature amount decoded in step S412 with the received feature amount (S416). Thereafter, the processing is substantially the same as in FIG. 5, but the modification detection unit 310 does not modify the protected area if the difference between the decoded feature quantity and the received feature quantity is within a predetermined range. Determine (S417). If the difference exceeds the predetermined range, it is determined that the protected area is altered (S418). Then, the verification result transmission unit 311 transmits the verification result of whether or not there is a modification to the image processing apparatus 101 (S419), and the verification result reception unit 312 receives the verification result of whether or not there is a modification (S407).

  Further, the first modification and the second modification are combined, and the background pattern or the entire image data of the document image is transmitted from the image processing apparatus 101 to the image processing apparatus 102 according to the data size of the image data of the document image. When all the image data is transmitted, the image processing apparatus 102 can extract the feature amount.

  In the above-described embodiments and modifications, it has been described that the presence or absence of modification is verified. However, the verification result is not limited to the presence or absence of alteration, but also includes the positional information of the protected area, the difference in the feature amount indicating the possibility of alteration, and the margin of the feature amount difference with respect to a predetermined range for determining the presence or absence of alteration. Degrees etc. can be included. In this case, it is not determined that there is a modification, but if there is a possibility of modification, it can be communicated to the user of the image processing apparatus 101 via the UI indicating the protected area of the document image. become.

[Other Examples]
The present invention can also be realized by executing the following processing. That is, software (program) that realizes the functions of the above-described embodiments is supplied to a system or apparatus via a network or various storage media, and a computer (or CPU, MPU, etc.) of the system or apparatus reads the program. It is a process to be executed.

Claims (13)

An information processing system comprising first and second devices, distributed to the first and second devices,
An input means for inputting a document image;
Background pattern extraction means for extracting a background pattern from the document image;
Decoding means for decoding position information and feature amount of a predetermined area of the document image from the background pattern;
A partial image extracting means for extracting an image of a region of the document image corresponding to the position information as a partial image;
A feature amount extracting means for extracting a feature amount of the partial image;
An information processing system comprising: verification means for comparing the extracted feature quantity with the decoded feature quantity to verify alteration of the area of the document image corresponding to the position information. The first device includes the input unit, the background pattern extraction unit, the unit that transmits the background pattern to the second device, the unit that receives the position information from the second device, and the partial image Extraction means, means for transmitting the partial image to the second device,
The second device receives means for receiving the background pattern from the first device, the decoding means, means for sending the position information to the first device, and receives the partial image from the first device. 2. The information processing system according to claim 1, further comprising: means for extracting, means for extracting the feature quantity, and means for verifying.   3. The image processing system according to claim 2, wherein the background pattern extraction unit extracts the background pattern as a binary image. The first apparatus further includes a determination unit that determines a data size of the document image, and when the data size of the document image is determined to be equal to or smaller than a predetermined size,
The first apparatus has the input means, means for transmitting the document image to the second apparatus,
The second apparatus includes means for receiving the document image from the first apparatus, background pattern extraction means, decoding means, partial image extraction means, feature quantity extraction means, and verification means. 2. The information processing system according to claim 1, further comprising: When it is determined that the data size of the document image exceeds the predetermined size,
The first device includes the input unit, the background pattern extraction unit, the unit that transmits the background pattern to the second device, the unit that receives the position information from the second device, and the partial image Extraction means, means for transmitting the partial image to the second device,
The second device receives means for receiving the background pattern from the first device, the decoding means, means for sending the position information to the first device, and receives the partial image from the first device. 5. The information processing system according to claim 4, further comprising means for extracting, means for extracting the feature quantity, and means for verifying.   6. The first device according to claim 4, further comprising a setting unit configured to set the predetermined size based on a communication amount and / or calculation performance of the first device. Information processing system. The first device includes the input unit, the background pattern extraction unit, the unit that transmits the background pattern to the second device, the unit that receives the position information from the second device, and the partial image Extraction means, extraction means for the feature quantity, means for transmitting the feature quantity to the second device,
The second device is configured to receive the background pattern from the first device, the decoding unit, a unit that transmits the position information to the first device, and the feature amount from the first device. 2. The information processing system according to claim 1, further comprising means for performing verification and the verification means.   8. The information processing system according to claim 2, wherein the second device further includes means for transmitting the verification result to the first device.   9. The information processing system according to claim 8, wherein the first device further includes means for receiving the verification result from the second device.   10. The information processing system according to claim 1, wherein the position information indicates an area of the document image to be protected from the alteration. An information processing method for an information processing system having input means, background pattern extraction means, decoding means, partial image extraction means, feature quantity extraction means, and verification means distributed in the first and second devices. ,
The input means inputs a document image;
The background pattern extraction means extracts a background pattern from the document image;
The decoding means decodes position information and feature amounts of a predetermined area of the document image from the background pattern,
The partial image extraction means extracts an image of the region of the document image corresponding to the position information as a partial image;
The feature quantity extraction means extracts the feature quantity of the partial image;
The information processing method characterized in that the verification means compares the extracted feature quantity with the decoded feature quantity to verify alteration of the region of the document image corresponding to the position information.   A program for causing a computer to function as the first and second devices according to any one of claims 1 to 10.   13. A computer-readable recording medium storing the program according to claim 12.

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